The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Extensive engineering and design effort is currently directed to hybrid powertrains for motor vehicles, especially passenger cars. One of the most promising and active areas involves the addition of an electric motor and associated electronic controller to a motor vehicle powertrain to supplement torque for launches in order that a smaller internal combustion engine may be utilized in the vehicle. Lower horsepower and smaller displacement engines routinely provide improved fuel economy over larger engines and, when supplemented by an electric motor for vehicle launch, provide entirely satisfactory overall performance.
Accordingly, many hybrid powertrains begin as adaptations of conventional and existing powertrains utilizing an internal combustion engine and a transmission having a torque converter and multiple planetary gear assemblies. Into this powertrain is added an electric motor and an appropriate launch and disconnect clutch. Frequently, the torque converter is removed. The addition is not without significant challenges, including launch strategies that minimize wear and heat losses with launch clutches.
The present invention is directed to a launch strategy for a hybrid powertrain which addresses and solves the above-delineated challenges.